FUNCTIONAL DESCRIPTION

PIN DEFINITIONS

Copyright ©1997-2001 Semtech Corporation

DOC5-418-DS-109

www.semtech.com

3

functionally of seven major sections

shown in the functional diagram on

the previous page: the keyboard

encoder, a 16-bit timer, the mode

control unit, the data buffer, the

interrupt control, the PC commun-

ication channel and the 8042

emulation channel. All sections

communicate with each other and

operate concurrently.

Mnemonic

DIP PLCC

QFP

Type Name and Function

VCC

40

44

38

I

Power Supply: +5V

VSS (GND)

20

22

17

I

Ground

OSCI

39

43

37

I

Oscillator input

OSCO

38

42

36

O

Oscillator output

_RESET

1

1

41

I

Reset: apply 0V to provide orderly start-up

EKC1

37

41

35

I

External Keyboard Clock 1:connects

to external keyboard clock line and is used

to generate an interrupt for every clock line

transmission

VX

3

4

43

I

Tie to VCC

VXA

3

I

Tie to VCC

RP

6

7

2

I

Tie to VCC

KC

8

9

4

I/O

Keyboard Clock: connects to

PC keyboard port clock data line

KD

7

8

3

I/O

Keyboard Data: connects to PC port

data line

EKD

10

11

6

I/O

External Keyboard Data: connect to

external keyboard data line

EKC

9

10

5

I/O

External Keyboard Clock: connects

to external keyboard clock line

_IRQ

2

2

42

I/O

Interrupt Line: reserved for low power

applications

R0-R5

29-34

32-37

27-32

I

Row Data Inputs

R6

5

6

1

I

R7

36

39

34

I

R7A

40

I

C0-C4

12-16

13-17

8-12

O

Column Select Outputs: select one of

C5-C7

17-19

19-21

13-15

O

16 columns

C8-C15

28-21

31-24

26-23

O

21-18

O

C4A

18

O

CL

11

12

7

O

Caps Lock LED

NL

4

5

44

O

Num Lock LED

SL

35

38

33

O

Scroll Lock LED

NC

23

39-40

No Connects: these pins are unused

16, 22

Note: An underscore before a pin mnemonic denotes an active low signal.

The controller continuously scans a

keyboard organized as an 8 row by

16 column matrix for a maximum of

128 keys. Smaller-size keyboards

are supported provided that all

unused row lines are pulled to Vcc.

The controller selects one of the 16

column lines (C0-C15) every 512

microseconds and then reads the

row data lines (R0-R7). A key

closure is detected as a zero in the

corresponding position of the

matrix.

A complete scan cycle for the entire

keyboard takes approximately 9.2

mS. Each key found pressed is

debounced for a period of 20 mS.

Once the key is verified, the

corresponding key code(s) are

loaded into the transmit buffer of the

PC communication channel.

Status LED indicators

The controller provides an interface

for three LED shift status indicators.

All three pins are active low to

indicate the status of the host

system (Num Lock, Caps Lock and

Scroll Lock) and are set by the

system.

Scan Code Table Sets

The UR5HC418 supports all three scan code table sets. Scan code table

set 3 allows the user to program individual key attributes such as

make/break and Typematic or single-touch action. For more information,

refer to the IBM Technical Reference Manuals. Custom scan code tables,

including macros, are also available.

Switch Matrix Encoding

Each matrix location is programmed to represent either a single key or a

key combination of the IBM 101/102/104 standard keyboard.

KEYBOARD ENCODER

KEYBOARD ENCODER, (CON’T)